package org.util;

import java.util.Random;

/**
 * 随机数、随即字符串工具
 * User: leizhimin
 * Date: 2008-11-19 9:43:09
 */
public class RandomUtils {
	 public static final String allChar = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";
	    public static final String letterChar = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";
	    public static final String numberChar = "0123456789";

	    /**
	     * 返回一个定长的随机字符串(只包含大小写字母、数字)
	     *
	     * @param length 随机字符串长度
	     * @return 随机字符串
	     */
	    public static String generateString(int length) {
	        StringBuffer sb = new StringBuffer();
	        Random random = new Random();
	        for (int i = 0; i < length; i++) {
	            sb.append(allChar.charAt(random.nextInt(allChar.length())));
	        }
	        return sb.toString();
	    }

	    /**
	     * 返回一个定长的随机纯字母字符串(只包含大小写字母)
	     *
	     * @param length 随机字符串长度
	     * @return 随机字符串
	     */
	    public static String generateMixString(int length) {
	        StringBuffer sb = new StringBuffer();
	        Random random = new Random();
	        for (int i = 0; i < length; i++) {
	            sb.append(allChar.charAt(random.nextInt(letterChar.length())));
	        }
	        return sb.toString();
	    }

	    /**
	     * 返回一个定长的随机纯大写字母字符串(只包含大小写字母)
	     *
	     * @param length 随机字符串长度
	     * @return 随机字符串
	     */
	    public static String generateLowerString(int length) {
	        return generateMixString(length).toLowerCase();
	    }

	    /**
	     * 返回一个定长的随机纯小写字母字符串(只包含大小写字母)
	     *
	     * @param length 随机字符串长度
	     * @return 随机字符串
	     */
	    public static String generateUpperString(int length) {
	        return generateMixString(length).toUpperCase();
	    }

	    /**
	     * 生成一个定长的纯0字符串
	     *
	     * @param length 字符串长度
	     * @return 纯0字符串
	     */
	    public static String generateZeroString(int length) {
	        StringBuffer sb = new StringBuffer();
	        for (int i = 0; i < length; i++) {
	            sb.append('0');
	        }
	        return sb.toString();
	    }

	    /**
	     * 根据数字生成一个定长的字符串，长度不够前面补0
	     *
	     * @param num       数字
	     * @param fixdlenth 字符串长度
	     * @return 定长的字符串
	     */
	    public static String toFixdLengthString(long num, int fixdlenth) {
	        StringBuffer sb = new StringBuffer();
	        String strNum = String.valueOf(num);
	        if (fixdlenth - strNum.length() >= 0) {
	            sb.append(generateZeroString(fixdlenth - strNum.length()));
	        } else {
	            throw new RuntimeException("将数字" + num + "转化为长度为" + fixdlenth + "的字符串发生异常！");
	        }
	        sb.append(strNum);
	        return sb.toString();
	    }

	    /**
	     * 根据数字生成一个定长的字符串，长度不够前面补0
	     *
	     * @param num       数字
	     * @param fixdlenth 字符串长度
	     * @return 定长的字符串
	     */
	    public static String toFixdLengthString(int num, int fixdlenth) {
	        StringBuffer sb = new StringBuffer();
	        String strNum = String.valueOf(num);
	        if (fixdlenth - strNum.length() >= 0) {
	            sb.append(generateZeroString(fixdlenth - strNum.length()));
	        } else {
	            throw new RuntimeException("将数字" + num + "转化为长度为" + fixdlenth + "的字符串发生异常！");
	        }
	        sb.append(strNum);
	        return sb.toString();
	    }

	    public static void main(String[] args) {
	        System.out.println(generateLowerString(5));
	        //System.out.println(toFixdLengthString(123, 5));
	    }
}
